The proposed work concerns isolation and characterization of several components of the renin angiotensin system. Of the primary importance is the renin substrate (angiotensinogen) for which a direct radioimmunoassay is being developed. Kinetic parameters of the renin reaction, using purified human angiotensinogen and homologous renin, will be determined and the influence of plasma from hypertensive and normal subjects on these kinetic parameters will be investigated. Studies are also to be undertaken to isolate substances from plasma and tissues which alter the kinetics of the renin reaction. These studies will include correlation of the renin activation phenomenon with experimental and pharmacological alterations of blood pressure in experimental animals (monkey) and man. Another area of investigation will be to isolate, by affinity chromatography, tissue proteins (receptors) which bind angiotensin peptides and characterize these proteins by physical and immunological techniques and evaluate their respective specificities. BIBLIOGRAPHIC REFERENCES: Sambhi, M.P.: Activators and inhibitors of Renin Angiotensin System. Book Chapter, In International Text Book of Hypertension. Editor, J. Genest, McGraw Hill, 1976. Dwarkanathan, A., Sambhi, M.P., Eggena, P. and Barrett, J.D.: Marked elevation of plasma renin activity during post diuretic sodium conservation in furosemide stimulated subjects. Res. Comm. in Chem. Path. and Pharmacology 3:581, March 1975.